ULTRASTRUCTURE OF THE METABASIDIUM OF AURICULARIA FUSCOSUCCINEA

Abstract

Maturation of the metabasidium of Auricularia fuscosuccinea was followed with light microscopy and transmission electron microscopy. The basidium was divided into four compartments by septa which developed centripetally as in hyphae. Each septum formed a septal pore apparatus with imperforate pore caps. A band of electron‐dense material was situated in the middle of the septal pore. There was a large increase in the volume of cytoplasm, excluding vacuoles, in each compartment during sterigmal outgrowth. Compartments were evacuated in basipetal sequence and vacuole enlargement began at the base of a compartment only when sterigmal formation was well advanced. The septal pore apparatus was intact until late in maturation of a compartment when septal swellings occluded the pore. The metabasidial wall was differentiated from those of other hymenial and subhymenial cells. The pattern of basidial maturation is compared with that in other phragmobasidiate and holobasidiate fungi. Use of the septal pore apparatus for phylogenetic and taxonomic purposes is discussed, as is the concept of primary and adventitious septa.